Spark-plug.



A. SCHMIDT.

SPARK PLUG.

APPLICATION FILED 1AN.lI, 1912.

Patented June 19, 1917.

' UNITED STATES PATENT anion.

ALBERT SCHMIDT, 0F FLINT, MICHIGAN, ASSIGNOR TO CHAMPION IGNITION COMPANY, OF FLINT, MICHIGAN, A CORPORATION OF MICHIGAN.

SPARK-PLUG.

Specification of Letters Patent.

Patented June 19,1917.

Application filed January 11, 1917. Serial No. 141,827,

To all whom it may concern:

' Be it known that I, ALBERT SCHMIDT, a citizen of the Republic of France, residing at Flint, in the county of Genesee and State of Michigan, have invented certain new and useful Improvements in Spark-Plugs, of which the following is a specification, reference being had therein to the accompanying drawings.

The invention relates to spark-plugs more particularly designed for use in high-speed engines where subjected to high heat when in operation, and it is the object of the invention to obtain a construction that will 0p erate satisfactorily under such conditions.

In the drawings:

Figure 1 is a longitudinal section through the plug;

Fig. 2 is a perspective view of the inner insulator member detached. A is the metallic casing provided with a seat or shoulder B. C is the insulator having an enlargement D for engaging the shoulder B and secured thereto by a flange E or other suitable means, so as to form a mechanically secure and gas-tight joint. The insulator C terminates short of the inner end of the casing A, and forms the sup port and securing means for an electrode F. This electrode is provided with a head or collar G bearing against the inner end of the insulator, and a shank portion which extends outward through the insulator, being secured by the nut H or other-suitable means. I is an inward projection of the electrode, extending into operative relation to the grounded electrode J.

' It is the primary object of the invention to mechanically support and insulate the electrode F by the insulator C, and at the same time to provide a mechanically independent insulator for forming the walls of the combustion chamber and protecting the electrode from short circuiting. Inasmuch as this inner insulation is exposed to very high heat the expansion and contraction that takes place therein is very different from that occurring in the outer insulator C, and it is therefore desirable that the support for the inner insulator should be entirely independent from that for the outer one. This I have accomplished by forming the casing A with a conical seat K at its inner end, on which the inner tubular insulator L is placed, said insulator being of a corresponding conical or tapering form. The insulator L may be formed of material which is highly refractory and can safely be subjected to the intense heat in the combustion chamber, but it is not essential that this material should be highly dielectric. For completing the electrical insulator a sleeve M of mica is placed between the inner insulator L and the casing A, said sleeve being extended to bridge the gap between the inner and outer insulators and to overlap the same. The insulator L when placed in position is secured by turning over a flange N on the cars ing, which will hold it from outward dis-' placement, while the conical seat will hold it from inward displacement. Thus the'insulator L is entirely independent in its sup port from the insulator C and can expand or contract without aflecting'the outer insulator or disturbing the gas-tight seal between the same and the outer casing and electrode. Furthermore, as the inner electrode is. supported by the conicalseat, a slight gap may be left between the same and the metallic collar G, as indicated at O, which will avoid heat conduction from the one to theother and thereby will protect said metallic collar from the direct heat'of the explosion chamber. In operation, the heat from the combustion gases in contact with the innerinsulator L will be conducted outward therethrough into the casing A, which is maintained at a comparatively low temperature by its connection with the water-jacketed enginecasing. The heat imparted from said combustion gases to theelectrode I will be conducted inward, a portion passing through the shank F and into the body of the insulator O, and another portion passing outward through the metallic collar G and into the end of the insulator C, or outward into the metallic casing A. Thus the heat of the inner insulator is dissipated almost entirely through the outer casing, while the heat of the electrode is dissipatedchiefly through the outer insulator. By reason of this division overheating of the outer insulator is avoided and there is less danger of cracking or destroying the gas-tight seal.

What I claim as my invention is:

1. In a spark-plug, the combination with a metallic casing, of an insulator mechani cally secured and sealed therein and terrni-' nating short of the inner end of said casing, an electrode mechanically supported and sealed in said insulator, and an inner insulator independently seated in said metallic casing, forming a shield for said outer insulator but having no mechanicalbearing thereon.

2. In a spark-plug, the combination with a casing, of an insulator mechanicall secured and sealed within said casing and erminating short of the inner end thereof, an electrode mechanically secured and sealed in said insulator, an inner tubular insulator having a conical outer face engaging a conical seat on said outer casing, and means on said casing for holding said insulator against said seat to support the same independently 0 said outer insulator and electrode.

3. In a spark-plug, the combination with an outer casing, of an insulator mechanically secured and sealed in said casing and terminating short of the inner end thereof, an

electrode extending through said insulator and having a metallic head or collar seated on the inner end thereof, an inner insulator extending into proximity to said head or collar on the electrode and protecting the same from the direct heat of combustion, said inner insulator being provided with a'conical Suter face for engaging a conical seat on the outer casing, and means on said outer casing for engaging the inner end of said insulator to hold the same to its seat, whereby said in sulators are mechanically independent of each other.

4. In a spark-plug, the combination with an outer casing, of an insulator mechanically secured and sealed within said casing and terminating short of the inner end thereof, an electrode passin through saidinsulator and having a hea I or collar engaging the inner end thereof and an inwardly-extendin portion, an inner insulator of tubular form havinga conical outer face for engaging a corresponding conical seat on the outer casing, a sleeved insulator between both the outer and inner insulators and the metallic casing, bridging the gap therebetween, and

means on thecasing for engaging the inner end of said inner insulator to hold the same I to its seat. a

5. In a spark-plug, the combination with an outer casing, of an outer insulator mechanically secured and sealed within said casing and terminating short of the inner end thereof, an electrode passin through said insulator and having a hea or collar engaging the inner end thereof and an inwardly-extending portion, an inner insulator extending lnto proximity to, said head or collar on the electrode and protecting the same from the direct heat of combustion, said in-. 

